01 - Preheat oven to 425°F and line a large baking sheet with parchment paper.
02 - In a large bowl, combine harissa paste, olive oil, smoked paprika, ground cumin, salt, black pepper, and minced garlic; mix thoroughly.
03 - Add chicken thighs to the bowl and toss to coat evenly with marinade. Let rest for at least 10 minutes or refrigerate up to 2 hours for enhanced flavor.
04 - Place sweet potato cubes and red onion wedges on the prepared baking sheet. Drizzle with olive oil, season lightly with salt and pepper, toss gently to coat, and spread in an even layer.
05 - Arrange the marinated chicken thighs atop the vegetables evenly.
06 - Roast in the preheated oven for 40 to 45 minutes until the chicken reaches an internal temperature of 165°F and sweet potatoes become tender and caramelized.
07 - Transfer to serving plates, garnish with chopped cilantro or parsley, and accompany with lemon wedges.